Evaluating and grading meat animals, both live and slaughtered, has historically been performed by humans. Because of this it is very difficult to achieve accuracy, efficiency and consistency. Both producers and packers demand an objective means of classifying their animals accurately according to their carcass real values. However, since an accurate, quick, and consistent grading system has not been put into place, producers are not being paid for the true value of their animals. Currently, producers are paid on an average basis. The price differential between a high-yield and a low-yield grade is less than it should be. Therefore, it is important to the hog and beef industries that improved or new technologies must be developed in their evaluation systems in order to be able to accurately measure the hog and beef carcass characteristics that are of significant value.
Labor costs and inconsistent grading are significant problems in the meat processing industry. Attempts have been made to automate the grading and inspection systems involved in meat processing. For example see U.S. Pat. No. 4,931,933, entitled, "Application of Knowledge-Based System for Grading Meat" granted to Chen et al, and U.S. Pat. No. 5,079,951, entitled "Ultrasonic Carcass Inspection" granted to Raymond et al. However, these systems are overly complicated and do not provide an efficient method of accurately measuring the Longissimus dorsi muscle depth and fat composition.
The Longissimus dorsi muscle is one of the most valuable portions of beef or pork and is also an excellent indication of the value of the rest of the animal or carcass. Therefore, most analysis of animals or carcasses with ultrasound concentrates on this muscle.
Ultrasonic images of the Longissimus dorsi (rib eye muscle in beef and loin eye muscle in hogs) have been used to evaluate livestock. U.S. Pat. No. 5,339,815 (Liu et al.) discloses a method and apparatus wherein an ultrasonic transducer is centered in a longitudinal direction over the last few ribs of the animal or carcass and the ultrasonic image is of a ribline, a Longissimus dorsi muscle and fat layers above the muscle such that the specified window starts below the ribline of the animal or carcass. A fat depth is determined from a distance between the second interface line and a specified plane of contact between the animal or carcass and the ultrasonic transducer adjusted for any positioning equipment or stand-off gel. A muscle depth is determined from a distance between the first and second interfaces line. The output of the system includes the fat depth and the muscle depth for the animal or carcass from which the image was taken.
Longissimus dorsi or ribeye muscle cross-sectional area is currently obtained by manually tracing around the perceived outline of the muscle from an ultrasonic image. Some ultrasonic scanners, like the latest model we have been using [Aloka, 1990a], provide the capability of approximating the area with an ellipse. Due to its low degree of accuracy and the relatively large time requirement, this feature is seldom used. It is, however, more common for the images to be recorded on a video tape and the area analysis done at a later time. This analysis is still a very time consuming process. Because of the quality of the image, accurately tracing the l.d. muscle area can be done only by trained technicians. It is, therefore, very difficult to achieve efficiency, consistency and accuracy. The teachings of U.S. Pat. No. 5, 339,815 provided a method to automatically determine the area of the muscle when the ultrasonic scan image input is transverse with respect to a backbone of the animal or carcass. However, there are faster and easier methods for measuring the width of the muscle.